Multimode Network Representation of Two Dimensional Steps in Rectangular Waveguides

In this paper a new Multimode Network representation for arbitrary rectangular waveguide junctions is presented. The energy coupling between the higher order modes excited in the junction is rigorously described via a multimode impedance matrix representation that can be used to build very efficient and accurate software tools for the analysis of complex structures. The elements of the impedance matrix are obtained from the solution of an integral equation. The main feature of the approach is that the kernel of the integral equation derived is essentially independent from frequency and therefore, the most time consuming task, namely the solution of the integral equation, need to be performed only once per each geometry. The formulation of the method is discussed and the form of the integral equation is given, showing explicitly the dependence with the frequency. A frequency extraction procedure that can lead to a considerable time saving for the analysis of complex structures is also discussed. Finally the design of a commercial communication satellite filter structure is presented, including comparisons between our analysis and measurements of the manufactured hardware.